The Effect of Motion Path on the Wear Rate of UHMWPE for Orthopaedic Implants

Mapping Intimacies â—½  
1999 â—½  
Author(s):  
Jeff A. Sprague â—½  
Willard L. Sauer
Keyword(s):  
Wear Rate â—½  
Wear Test â—½  
Axial Rotation â—½  
Wear Testing â—½  
Motion Path â—½  
Orthopaedic Implant â—½  
Wear Rates â—½  
Nonlinear Motion â—½  
Pin On Disk

Abstract The effect of adding a second axis of motion was investigated for pin-on-disk wear testing of ultra-high-molecular-weight polyethylene (UHMWPE) for orthopaedic implant applications. In addition to linear reciprocation of the UHMWPE or metal disk, axial rotation of the metal or UHMWPE pin was conducted. The added rotation reproduces the cross-shear on the UHMWPE surface that is generated in clinically relevant wear simulator tests and in vivo. The wear rates that result from the multi-axis pin-on-disk tests are significantly higher (one to two orders of magnitude) than those seen in the linear-only tests. This supports the findings of other researchers (Bragdon et al., 1996; McKellop, 1995; Walker et al., 1996; Wang et al. 1997) in that the application of nonlinear motion increases the wear of UHMWPE substantially. This is further validated by the comparison of a hip simulator wear test conducted with three axes of motion — rotation, flexion, and abduction — to a test conducted with two axes of motion — rotation and flexion. The absence of the abduction eliminated a significant degree of nonlinear motion (cross-shear) and, consequently, the wear rate was significantly lower than that seen in the test with abduction.

Wear simulation of the ProDisc-L disc replacement using adaptive finite element analysis

2007 â—½  
Vol 7 (2) â—½  
pp. 165-173 â—½  
Author(s):  
Jeremy J. Rawlinson â—½  
Karan P. Punga â—½  
Kirk L. Gunsallus â—½  
Donald L. Bartel â—½  
Timothy M. Wright
Keyword(s):  
Finite Element â—½  
Wear Rate â—½  
Axial Load â—½  
Computational Simulation â—½  
Wear Test â—½  
Wear Testing â—½  
Adaptive Finite Element â—½  
Wear Rates â—½  
Specific Loading â—½  
Flexion Extension

Object. An understanding of the wear potential of total disc replacements (TDRs) is critical as these new devices are increasingly introduced into clinical practice. The authors analyzed the wear potential of a ProDisc-L implant using an adaptive finite element (FE) technique in a computational simulation representing a physical wear test. Methods. The framework for calculating abrasive wear, first validated using a model of a total hip replacement (THR), was then used to model the ProDisc-L polyethylene component that is fixed to the inferior endplate and articulates with the rigid superior endplate. Proposed standards for spine wear testing protocols specified the inputs of flexion–extension (6/−3°), lateral bending (± 2°), axial twist (± 1.5°), and axial load (200–1750 N or 600–2000 N) applied to the model through 10 million simulation cycles. The model was calibrated with a wear coefficient determined from an experimental wear test. Implicit FE analyses were then performed for variations in coefficient of friction, polyethylene elastic modulus, radial clearance, and polyethylene component thickness to investigate their effects on wear. Results. Using the initial loading protocol (single-peaked axial load profile of 300–1750 N) from the experimental wear test, the polyethylene wear rate was 9.82 mg per million cycles. When a double-peaked loading profile (600–2000 N) was applied, the wear rate increased to 11.77 mg per million cycles. Parametric design variations produced only small changes in wear rates for this simulation. Conclusions. The chosen design variables had little effect on the resultant wear rates. The comparable wear rate for the THR validation analysis was 16.17 mg per million cycles, indicating that, using this framework, the wear potential of the TDR was equivalent to, if not better, than the THR using joint-specific loading standards.

Wear of Artificial Joint Materials III

1981 â—½  
Vol 10 (3) â—½  
pp. 137-142 â—½  
Author(s):  
R W Treharne â—½  
R W Young â—½  
S R Young
Keyword(s):  
Wear Rate â—½  
Contact Area â—½  
Inverse Relationship â—½  
Wear Testing â—½  
Artificial Joint â—½  
Knee Prostheses â—½  
Wear Rates â—½  
Knee Simulator â—½  
Total Knee

This paper describes a new method for testing total knee prostheses under simulated in vivo conditions. Previous knee simulator work has been summarized and described. The major variables of testing are also described in detail. The results of wear testing five types of knee prostheses were that the wear rate was nearly an inverse relationship with contact area— knees with a higher contact area had lower wear rates.

Determination of Steady-State Adhesive Wear Rate

2005 â—½  
Author(s):  
L. J. Yang
Keyword(s):  
Steady State â—½  
Wear Rate â—½  
Wear Test â—½  
Standard Test â—½  
Test Method â—½  
Testing Time â—½  
Wear Coefficient â—½  
Wear Rates â—½  
Test Methodology

Wear rates obtained from different investigators could vary significantly due to lack of a standard test method. A test methodology is therefore proposed in this paper to enable the steady-state wear rate to be determined more accurately, consistently, and efficiently. The wear test will be divided into four stages: (i) to conduct the transient wear test; (ii) to predict the steady-state wear coefficient with the required sliding distance based on the transient wear data by using Yang’s second wear coefficient equation; (iii) to conduct confirmation runs to obtain the measured steady-state wear coefficient value; and (iv) to convert the steady-state wear coefficient value into a steady-state wear rate. The proposed methodology is supported by wear data obtained previously on aluminium based matrix composite materials. It is capable of giving more accurate steady-state wear coefficient and wear rate values, as well as saving a lot of testing time and labour, by reducing the number of trial runs required to achieve the steady-state wear condition.

scholarly journals Properties of Ion Implanted Ti-6Al-4V Processed using Beamline and PSII Techniques

MRS Proceedings â—½  
1996 â—½  
Vol 438 â—½  
Author(s):  
K. C. Walter â—½  
J. M. Williams â—½  
J. S. Woodring â—½  
M. Nastasi â—½  
D. B. Poker â—½  
...  
Keyword(s):  
Wear Rate â—½  
Dose Level â—½  
Surface Hardness â—½  
Plasma Source â—½  
Wear Testing â—½  
Nitrogen Gas â—½  
Plasma Source Ion Implantation â—½  
Boron Implantation â—½  
Pin On Disk â—½  
Disk Method

AbstractThe surface of Ti-6Al-4V (Ti64) alloy has been modified using beamline implantation of boron. In separate experiments, Ti64 has been implanted with nitrogen using a plasma source ion implantation (PSII) technique utilizing either ammonia (NH 3), nitrogen (N2), or their combinations as the source of nitrogen ions. Beamline experiments have shown the hardness of the N-implanted surface saturates at a dose level of ˜4× 1017 at/cm2 at ˜10 GPa. The present work makes comparisons of hardness and tribological tests of (1) B implantation using beamline techniques, and (2) N implanted samples using ammonia and/or nitrogen gas in a PSII process. The results show that PSII using N2 or NH3 gives similar hardness as N implantation using a beamline process. The presence of H in the Ti alloy surface does not affect the hardness of the implanted surface. Boron implantation increased the surface hardness by as much as 2.5x at the highest dose level. Wear testing by a pin-on-disk method indicated that nitrogen implantation reduced the wear rate by as much as 120x, and boron implantation reduced the wear rate by 6.5x. Increased wear resistance was accompanied by a decreased coefficient of friction.

scholarly journals Wear Properties of Sc-Bearing Zr-Based Composite BMG with Nano-CuZr2 under Lubrication

Applied Sciences â—½  
10.3390/app10144909 â—½  
2020 â—½  
Vol 10 (14) â—½  
pp. 4909
Author(s):  
Shing-Hoa Wang â—½  
Chau-Chang Chou â—½  
Hsien-Hung Chung â—½  
Rong-Tan Huang â—½  
Horng-Yi Chang â—½  
...  
Keyword(s):  
Wear Rate â—½  
Wear Test â—½  
Surface Friction â—½  
Sample Surface â—½  
Optical Microscope â—½  
Wear Properties â—½  
Friction Coefficients â—½  
Adhesion Wear â—½  
Pin On Disk â—½  
New Phase

Lubricated sliding wear of amorphous (Zr55Cu30Ni10Al5)99.98Sc0.02/CuZr2 nanocrystal composite bulk metallic glasses (BMG) under various sliding velocities with a load of 20 N was investigated using the pin-on-disk test. After the wear test involving oil lubrication was performed, there was no wear induced new-phase transformation in the sample surface. Friction coefficients were within the range from 0.22 to approximately 0.29 under a 20-N load at different sliding velocities. Therefore, the calculated friction coefficients clearly indicated that the adhesion wear dominated from the experimental results. This deformation behavior resulted in a higher wear rate and wear coefficient. In addition, worn surfaces were characterized and examined under a scanning electron microscope (SEM) and optical microscope. The mechanism of high wear rate was clarified.

scholarly journals Competitive Binding of Bilirubin and Fatty Acid on Serum Albumin Affects Wear of UHMWPE

Lubricants â—½  
2020 â—½  
Vol 8 (5) â—½  
pp. 53
Author(s):  
Spencer Fullam â—½  
Jade He â—½  
Caroline S. Scholl â—½  
Thomas M. Schmid â—½  
Markus A. Wimmer
Keyword(s):  
Fatty Acid â—½  
Wear Rate â—½  
Conformational Change â—½  
Total Joint Replacement â—½  
Calf Serum â—½  
Competitive Binding â—½  
Wear Testing â—½  
Molar Ratio â—½  
Wear Rates â—½  
Uhmwpe Wear

Total Joint Replacement (TJR) devices undergo standardized wear testing in mechanical simulators while submerged in a proteinaceous testing solution to mimic the environmental conditions of artificial joints in the human body. Typically, bovine calf serum is used to provide the required protein content. However, due to lot-to-lot variability, an undesirable variance in testing outcome is observed. Based on an earlier finding that yellowish-orange serum color saturation is associated with wear rate, we examined potential sources of this variability, by running a comparative wear test with bilirubin; hemin; and a fatty acid, oleic acid, in the lubricant. All these compounds readily bind to albumin, the most abundant protein in bovine serum. Ultrahigh molecular weight polyethylene (UHMWPE) pins were articulated against CoCrMo discs in a pin-on-disc tribometer, and the UHMWPE wear rates were compared between lubricants. We found that the addition of bilirubin increased wear by 121%, while hemin had a much weaker, insignificant effect. When added at the same molar ratio as bilirubin, the fatty acid tended to reduce wear. Additionally, there was a significant interaction with respect to bilirubin and hemin in that UHMWPE wear rate decreased with increasing fatty acid concentration. We believe the conformational change in albumin by binding bilirubin makes it more likely to form molecular bridges between UHMWPE and the metal counterface, thus increasing adhesive wear. However, fatty acids compete for binding sites on albumin, and can prevent this conformational change. Hence, the protein is stabilized, and the chance for albumin to form bridges is lowered. Ultimately, UHMWPE wear rate is driven by the competitive binding of bilirubin and fatty acid to albumin.

The effect of femoral head diameter upon lubrication and wear of metal-on-metal total hip replacements

2001 â—½  
Vol 215 (2) â—½  
pp. 161-170 â—½  
Author(s):  
S L Smith â—½  
D Dowson â—½  
A A J Goldsmith
Keyword(s):  
Wear Rate â—½  
Boundary Lubrication â—½  
Wear Testing â—½  
Wear Rates â—½  
Surface Separation â—½  
Lubricating Film â—½  
Lubrication Regime â—½  
Metal On Metal â—½  
The Mean â—½  
Mixed Lubrication Regime

It has been found that a remarkable reduction in the wear of metal-on-metal hip joints can be achieved by simply increasing the diameter of the joint. A tribological evaluation of metal-on-metal joints of 16, 22,225, 28 and 36 mm diameter was conducted in 25 per cent bovine serum using a hip joint simulator. The joints were subject to dynamic motion and loading cycles simulating walking for both lubrication and wear studies. For each size of joint in the lubrication study, an electrical resistivity technique was used to detect the extent of surface separation through a complete walking cycle. Wear of each size of joint was measured gravimetrically in wear tests of at least 2 × 106 cycles duration. Joints of 16 and 22.225mm diameter showed no surface separation in the lubrication study. This suggested that wear would be proportional to the sliding distance and hence joint size in this boundary lubrication regime. A 28 mm diameter joint showed only limited evidence of surface separation suggesting that these joints were operating in a mixed lubrication regime. A 36 mm diameter joint showed surface separation for considerable parts of each walking cycle and hence evidence of the formation of a protective lubricating film. Wear testing of 16 and 22.225mm diameter metal-on-metal joints gave mean wear rates of 4.85 and 6.30mm3/106 cycles respectively. The ratio of these wear rates, 0.77, is approximately the same as the joint diameters ratio, 16/22.225 or 0.72, as expected from simple wear theory for dry or boundary lubrication conditions. No bedding-in was observed with these smaller diameter joints. For the 28 mm diameter joint, from 0 to 2 × 106 cycles, the mean wear rate was 1.62 mm3/106 cycles as the joints bedded-in. Following bedding-in, from 2.0 × 106 to 4.7 × 106 cycles, the wear rate was 0.54mm3/106 cycles. As reported previously by Goldsmith in 2000 [1], the mean steady state wear rate of the 36 mm diameter joints was lower than those of all the other diameters at 0.07 mm3/106 cycles. For a range of joints of various diameters, subjected to identical test conditions, mean wear rates differed by almost two orders of magnitude. This study has demonstrated that the application of sound tribological principles to prosthetic design can reduce the wear of metal-on-metal joints, using currently available materials, to a negligible level.

Performance analysis of an orthopaedic biomaterial 100-station wear test system

2009 â—½  
Vol 224 (3) â—½  
pp. 697-701 â—½  
Author(s):  
V Saikko
Keyword(s):  
Wear Rate â—½  
Polyethylene Wear â—½  
Calf Serum â—½  
High Capacity â—½  
Wear Test â—½  
High Standard â—½  
Test System â—½  
Wear Rates â—½  
Two Samples â—½  
The Mean

Until recently, wear studies of orthopaedic biomaterials have suffered from inadequate testing capacity and high standard deviation (SD) of results. In the present article, the previously validated 100-station hip wear simulator, the SuperCTPOD, is evaluated with regard to its capability of producing statistically significant differences in mean wear rates. SuperCTPOD wear tests were done for 38 different types of polyethylene pins against polished CoCr discs with diluted calf serum lubrication. A total of 200 pins were worn in two consecutive tests of 6 weeks, duration each. The sample size varied from four to six. The mean wear rates of the samples ranged from 0.52 to 77.1 mg per one million cycles. On the average, the SD of the wear rate was 4.2 per cent of the mean value (range 1–8.5 per cent). A difference in the mean wear rates below 5 per cent was large enough to be statistically significant ( p <0.05) in 21 comparisons between two samples, the lowest statistically significant mean difference being 3.2 per cent. In conclusion, the high capacity and the low SD of the wear rate make the SuperCTPOD wear test system unparalleled in efficiency. The observations regarding the effect of crosslinking and molecular weight on polyethylene wear resistance were in agreement with studies published earlier.

Defect Structures in Diamond Composite Coated Cemented Tungsten CarbideSubstrates

2011 â—½  
Vol 325 â—½  
pp. 339-344 â—½  
Author(s):  
Jim N. Boland â—½  
Xing S. Li â—½  
D. Hay â—½  
Colin M. MacRae â—½  
S. Elbracht â—½  
...  
Keyword(s):  
Wear Rate â—½  
Poor Quality â—½  
Wear Testing â—½  
Grinding Wheel â—½  
Sem Images â—½  
Volume Percentage â—½  
X Ray â—½  
Wear Rates â—½  
Valid Test â—½  
The Difference

Variability in the abrasive wear of PCD coatings on cemented WC substrates has been investigated. Six samples of PCD coated carbides were tested in a wear testing rig. The PCD coated element was used to turn an industry standard vitrified bonded corundum grinding wheel. The wear rate was measured as the weight loss of the cutting element per cubic metre of grinding wheel machined during the test. Two grades of cutting elements were observed. One grade had wear rates between 6 and 7.3 g/m³ but of the three poor quality samples, only one valid test was made realising wear rate of ~7,800 g/m³. The microstructures of the samples were studied using SEM, X-ray imaging, neutron diffraction and XRD. SEM images revealed differences in the volume percentage of diamonds in the two grades and the XRD scans highlighted the variable distribution of the diamond phase in the coating. Estimates of the residual stresses in a good and poor quality samples indicated significantly higher compressive stresses in the good quality versus poor quality coating. These results have revealed two extremes in the wear rates of these PCD coated carbides. It is suggested that the difference in diamond content between the two grades is not sufficient to account for the 3 orders-of-magnitude difference in the observed wear rates. However, the presence of intrusive veins of carbide material in the coatings, especially around the curved cutting tip, suggested that the macroscopic defects observed in the x-ray and SEM images were the major cause of the high wear rates in the poor quality sample.

Load Scenarios Influence Fluid Absorption of Polyethylene

2005 â—½  
Author(s):  
T. Schwenke â—½  
C. Rieker â—½  
M. A. Wimmer
Keyword(s):  
Wear Testing â—½  
Fluid Absorption â—½  
Joint Replacements â—½  
Wear Rates â—½  
Total Joint Replacements â—½  
Fluid Uptake â—½  
Dynamically Loaded â—½  
Low Wear â—½  
Lubrication Conditions

Wear of total joint replacements is determined gravimetrically in simulator studies. A mix of bovine serum, distilled water, and additives is intended to replicate the lubrication conditions in-vivo. Weight gain due to fluid absorption during testing of UHMWPE components is corrected using a load soak station. In this study six sets of UHMWPE pins were tested for their fluid soak behavior. The samples were subjected to three different loading scenarios while being submersed in two types of commonly used lubricants. After two million cycles or 23.1 days, respectively, the different fluids lead to significantly different soaking results. Test groups that were dynamically loaded gained more weight than unloaded or statically loaded samples. The results suggest that dynamically loaded soak control stations are required during wear testing of UHMWPE components. Otherwise the fluid uptake masks the wear measurement, especially for new polyethylene materials with low wear rates. Furthermore, an agreement on detailed lubricant specifications is desirable.

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